Relief-check assembly for directional control valve



Jan. 9, 1968 R. B. OLEN I 3,3 4

RELIEF-CHECK ASSEMBLY FOR DIRECTIONAL CONTROL VALVE Original Fil'd Jan.6, 19 5 2 Sheets-Sheet 1 FIG 3 uvvmnm ROBERT B. OLEN f Bbmmnk oomeuATTORNEYS Jan. 9, 1968 R. B. OLEN RELIEF-CHECK ASSEMBLY FOR DIRECTIONALCONTROL VALVE Original Filed Jan. 6. 1965 Sheets-Sheet FIGS FIG 4 FIG 6-INVENTOR. ROBERT E. OLEN ATTORNEYS United States Patent 3 362,430RELIEF-CHECK ASSEMBLY FOR DIRECTIONAL CONTROL VALVE Robert B. Olen,Akron, Ohio, assignor to Parker-Hannifin Corporation, leveland, Ohio, acorporation of hi0 Continuation of application Ser. No. 426,468, Jan. 6,1965, which is a continuation of application Ser. No. 114,471, June 2,1961. This application July 20, 1966, Ser. No. 568,701

9 Claims. (Cl. 137-596) The present invention is a continuation ofapplicants prior copending application Ser. No. 426,468, filed Jan. 6,1965, now abandoned, which is a continuation of application Ser. No.114,471, filed June 2, 1961, now abandoned, and relates generally asindicated to a relief-check assembly for a directional control valve andmore particularly to such assembly which may be made up as a separateunit for attachment to a conventional type of directional control valve.

In hydraulic systems wherein the hydraulic motors handle heavy loads,there are instances in which, when actutaion of the motor is arrested,the inertia of the load will build up a high shock pressure in thesystem between the hydraulic motor and the closed directional controlvalve. Continued movement of the load under such conditions also causescavitation in the fluid circuit between the hydraulic motor and theclosed directional control valve. Moreover, there maybe occasions inwhich the load changes from positive to negative whereby it may tend tomove faster than the system pump can supply fluid thereinto in whichcase cavitation may result in the inlet system and, furthermore,excessive pressure may build up in the fluid return system.

Accordingly, it is a principal object of this invention to provide arelief-check assembly which is disposed between the directional controlvalve and the fluid motor to preelude cavitation or excessive pressurebuild-up in the system, irrespective of whether such conditions may becaused by the directional control valve being shifted from an operatingposition to neutral position blocking the motor ports, or by loadshifting while the directional control valve is in an operatingposition.

Other objects and advantages of the present invention will becomeapparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawings setting forth in detail a certain illustrativeembodiment of the invention, this being indicative, however, of but oneof the various ways in which the principle of the invention may beemployed.

In said annexed drawings:

FIG. 1 is a side elevation view of a hydraulically operated overheadshovel loader in which the load on the boom actuating cylinder shiftsfrom positive to negative as the boom swings from the one side ofvertical position to the other side;

FIG. 2 is a front elevation view of a two-spool directional controlvalve having mounted thereon the reliefcheck assembly consistuting thepresent invention;

FIG. 3 is a side elevation view as viewed from the righthand side ofFIG. 2; I

FIG. 4 is a cross-section view through the directional control valveassembly taken substantially along the line 4-4, FIG. 3;

FIG. 5 is a cross-section view through the relief-check assembly takensubstantially along the line 5-5, FIG. 3;

FIG. 6 is a fragmentary detail cross-section view taken substantiallyalong the line 6-6, FIG. 5;

FIG. 7 is a fragmentary cross-section view through a pair ofrelief-check assemblies as associated with one of the directionalcontrol valves, such section having been taken substantially along theline 77, FIG. 5; and

FIG. 8 is an enlarged fragmentary detailed view of the upperrelief-check assembly of FIG. 5.

Referring now more particularly to the drawings, and first to FIG. 1,there is shown therein an overhead shovel loader 1 having a boomassembly 2 pivotally connected thereto at 3, there being a bucket orscoop 4 mounted at the end of said boom assembly 2. The boom assembly 2is adapted to be swung from the full line position to the dotted lineposition as by means of the hydraulic cylinder 5 which is mounted on atrunnion 6 and having its piston rod 7 pivotally connected to the boomassembly at 8. It can be seen that when the bucket 4 is filled and swungupward, the center of gravity of the boom assembly 2 and the load in thebucket 4 will pass over to the left side of the boom pivot 3, whereafterthe boom weight and load will change from positive to negative andthereby tend to pull the piston in the cylinder 5 toward the left andperhaps at a rate which exceeds the capacity of the engine driven pump(not shown). Similarly, the inertia of the load in shifting to negativemay build up a high pressure in the return system. FIG. 1 is, of course,merely an illustrative example of a case wherein the load moved by afluid motor may shift from positive to negative. Moreover, in FIG. 1when the loaded bucket 4 is lowered, and the, directional control valvefor the cylinder 5 is moved to neutral position, the inertia of the loadmay build up a high shock pressure in the fluid which is then trappedbetween the discharge end of the cylinder 5 and the now closeddirectional control valve. Likewise, such inertia and continued movementof the load may cause a partial vacuum to be formed in the intake sideof the cylinder 5 which also is blocked by the closed directionalcontrol valve.

Referring now more particularly to the present invention as disclosed inFIGS. 2 to 7, the directional control valve 10 is herein shown ascomprising a housing 11 in which two spool valves 12 and 14 are axiallyshiftable respectively to control the operation of, for example, adouble acting cylinder 15 and a single acting cylinder 16.

As is known in the art, and as best shown in FIGS. 2 and 4, the housing11 has a pressure inlet port 17 (in communication with the dischargeport of pump P) and inlet chamber 18, the latter of which communicateswith the feed passages 19 and 20 intersecting the bores 21 and 23 forthe respective spools 12 and 14 via the check valves 24 and 25 Thehousing 11 is also formed with a bypass passage 26 common to. the spoolbores 21 and 23, said bypass passage 26 communicating with the fluidreturn port 27 adapted for connection with a fluid reservoir R.

Straddling the respective feed passages 19 and 20 are the pairs ofservice ports 28-28 and 29-29 and the return passages 30-30. Anotherreturn passage 31 is provided, there being a relief valve 32 between theinlet chamber 18 and such return passage 31.

The spool 12 is formed with alternate lands and grooves and is hereinshown as being of the double acting, or four- 'way type, for actuationof.the double acting cylinder 15 connected to the service ports 28-28.When the spool 12 is in neutral position as shown in FIG. 4, fluid inthe inlet chamber 18 will freely bypass to the return port27 via thebypass passage 26. When the spool 12 is moved upwardly, the bypass 26 isclosed, and fluid under pressure in the inlet chamber 18 flows throughthe check valve 24 into the feed passage 19 and through the lowerservice port 28 into the rod end of the cylinder 15, and the fluiddisplaced from the head end of the cylinder 15 flows to the return port27 by way of the upper service port 28 and return passage 31). On theother hand, when the spool 12 is shifted downwardly, the upper serviceport 28 becomes the pressure outlet to the head end or the cylinder 15while the lower service port 28 becomes the return for the fluiddisplaced from the rod end of the cylinder 15, the bypass 26 again beingclosed.

One end of the spool 12 has associated therewith a spring returnmechanism 34 which automatically returns the spool 12 to neutralposition from either of its two operating positions. In the neutralposition, fluid is trapped between the service ports 2828 and the endsof the cylinder 15, whereby the piston 35 in the cylinder 15 is heldagainst movement in either direction.

With reference to the other spool 14, it is herein shown as being of thesingle acting, or three-way type, for actuating the single actingcylinder 16 and in that case only one service port 29 is required, theupper service port 29 being closed by plug 36. In the neutral positionof the single acting spool 14, the lower service port 29 is blocked,

whereby fluid is trapped between the cylinder 16 and the directionalcontrol valve, i.e., the free circulation of fluid from the inletchamber 18 to the return port 27. When the spool 14 is shifted upwardlyfrom the FIG. 4 position, the bypass passage 26 is closed thereby andfluid under pressure in the inlet chamber 18 is delivered to thecylinder 16 to raise the load on the piston 37 via the check valve 25,the feed passage 20, and the lower service port 29. On the other hand,when the spool 14 is shifted downwardly, the bypass 26 is again openedand the piston 37 with its load is allowed to descend with the fluidbeing drained through the return port 27 via the lower service port 29and return passage 30. The single acting spool 14 has associatedtherewith the same type of spring return mechanism 34 as used with thedouble acting spool 12.

It is to be understood that both spools 12 and 14 may be of the doubleacting type, or of the single acting type. Furthermore, there are othertypes of spools providing additional operating positions such as a floatposition, but for the purposes of the present invention such other typesof spool valves need not be illustrated.

With reference to the relief-check assembly 40, the same is herein shownas comprising a separate housing 41 secured as by screws 42 to thedirectional control valve housing 11 and provided with ports 2828 and2929 registering with the ports of housing 11 for connection with fluidmotors 15 and 16 as shown in FIG. 2.

In the case of the double acting spool 12, there are provided tworelief-check assemblies 43 and in the case of the single acting spool 14only one relief-check as sembly 43 is required, but space is providedfor another one in the event that a spool 14 of the double-acting typeis substituted. The relief-check housing 41 is provided with athree-branch return 45 which communicates with the return port 27 of thedirectional control valve housing 11 by way of the aligned passages 46and 47 (see FIGS. 5 and 6).

Referring to the pair of relief-check assemblies 43 used in connectionWith the double acting spool 12, the center branch of the return passage45 communicates with service ports 28-28 by way of the passages in seatbushings 48. A valve member 49 is urged by spring 50 into engagementwith each seat bushing 48 whereby fluid will be admitted into eitherservice port 28 if the pressure therein is less than in the returnpassage 45, as when there is a case of cavitation with the double actingcylinder demanding fluid that is either not available, or demanding morefluid than can be provided by the system pump.

Each valve member 49, however, in addition to functioning as a checkvalve, also constitutes a pilot-operated relief valve. As perhaps bestseen in FIG. 8, valve member 49 has an orifice 51 therethrough toequalize the fluid pressures in the chamber 52 and in the associatedservice port 28, whereby the valve member 49 will be seated by fluidunder pressure in chamber 52 and by the spring 50. Closing the chamber52 is a pilot relief valve 53 which is held in seated position by theadjustable spring 54. It can be seen that when the pressure in thechamber 52 exceeds the seating force on the pilot valve member 53, thechamber 52 will be vented to the return passage 45 more rapidly thanfluid can be replenished into the chamber 52 through the orifice 51.This, therefore, creates a pressure differential such that the valvemember 49 will be moved away from its seat thereby to relieve excesspressure in the associated service port 28 to the return passage 45.

In the case of the relief-check assembly 43 used in conjunction with thesingle acting spool 14, it is of the same construction as the pair ofassemblies 43 used with the double acting spool 12 and operates in thesame Way, that is, as a check valve when the pressure in the lowercylinder port 29 is less than in the return passage 45 and as a reliefvalve when the pressure in the lower cylinder port 29 is greater thanthat for which the pilot relief valve member 53 is set by the adjustablespring 54.

Referring now more particularly to the operation of the presentinvention, it can be seen that should the double acting spool 12 beallowed to shift to neutral position from one operating position fluidwill be trapped between the cylinder 15 and the service ports 2828 andshould the load on the piston 35 tend to continue to move by reason ofits inertia, the pressure will build up in what was the return circuitsuflicient to unseat the pilot relief valve 53 and thereby open thevalve member 49 to communicate the service port 28 to return passage 45.At the same time, cavitation in the other end of the cylinder 15 isprevented by opening of the other valve member 49 by lower pressure inthe associated service port 28 than in the return passage 45. Moreover,in the case of the double acting arrangement as shown in FIG. 5, therelieved fluid shooting across the return passage 45 will assist in theopening of said other valve member 49. Thus the latter is subjected toimpingement or dynamic fluid pressure as well as the static fluidpressures acting on the lower end thereof to aid in rapid opening ofsuch member 49. Arrangement of the two valve members 49 of an associatedpair of the same in opposed relation with a straight passagetherebetween further facilitates maximum utilization of such dynamicfluid pressures.

With reference to the operation of the relief-check assembly 43associated with the single acting spool 14, if the spool is allowed tomove from the position whereat the piston 37 is descending under load toneutral position, the inertia of the downwardly descending load on thepiston 37 will build up a substantial pressure in the fluid that is nowblocked by the single acting spool 14. However, the relief-checkassembly 43 herein acts as a pilot operated relief valve to allow excesspressure thus built up to pass into the return passage 45. If, on theother hand, the installation is such that the load on the piston 37 ismoved upwardly at a rapid rate, and the single acting spool 14 isallowed at that time, to move from operating position to neutralposition, then the tendency of the load to continue to move by inertiawill decrease the pressure in the fluid trapped between the spool 14 andthe cylinder 16 and at that time the pressure in the lower service port29 may become low enough with respect to the pressure in the returnpassage 45 as to cause opening of the valve member 49 functioning as acheck valve.

The relief-check assemblies 43 herein also function to relieve partialvacuum and/ or excessive pressure due to load shift from positive tonegative, or negative to positive, as exemplarily shown in FIG. 1. Thepilot relief valves 53 should be set to open at pressures at least asgreat as the main relief valve 32 so that the valve members 49 do notopen prematurely when heavy loads are handled on the pistons 35 and 37.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims, or the equivalent ofsuch, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In combination, a directional control valve comprising a housinghaving an inlet port for fluid under pressure, a return port, and a pairof service ports, and a valve member movable in said housing fromneutral position blocking fluid communication between said inlet portand both service ports to either of two operating positions selectivelycommunicating said service ports with said inlet and return ports; and apair of combination relief-check valve assemblies normally closingcommunication between the respective service ports and said return portand including spring-biased valve members arranged to be moved as checkvalve members by fluid under pressure in said return port of magnitudeexceeding that in the respective service ports to positions establishingfluid communication between said return port and the respective serviceports, and to be moved as relief valve members by fluid under pressurein the respective service ports of magnitude exceeding that in saidreturn port to a position similarly establishing fluid communicationbetween the respective service ports and said return port; said valveassemblies being oppositely disposed so that fluid under pressurerelieved by one spring-biased valve member from one service port to saidreturn port impinges on the other spring-biased valve member tending tomove the latter to establish fluid communication between said returnport and the other service port.

2. In combination, a directional control valve comprising a housinghaving an inlet port for fluid under pressure, a return port, and a pairof service ports, and a valve member movable in said housing fromneutral position blocking fluid communication between said inlet portand both service ports to either of two operating positions selectivelycommunicating said service ports with said inlet port and return port;conduits for establishing fluid communication between said inlet portand a discharge port of a pump and between said service ports and therespective ports of a double acting fluid motor; and a pair ofcombination relief-check assemblies normally closing communicationbetween the respective service ports and said return port and includingspring-biased valve members arranged to be moved as check valve membersby fluid under pressure in said return port of magnitude exceeding thatin the respective service ports to positions establishing fluidcommunication between said return port and the respective service ports,and to be moved as relief valve members by fluid under pressure in therespective service ports of magnitude exceeding that in said return portto a position similarly establishing fluid communication between therespective service ports and said return port, said valve assembliesbeing oppositely disposed so that fluid under pressure relieved by onespring-biased valve member from one service port to said return portimpinges on the other spring-biased valve member tending to move thelatter to establish fluid communication between said return port and theother service port.

3. In combination, a directional control valve comprising a housinghaving an inlet port for fluid under pressure, a return port, and a pairof service ports, and a valve member movable in said housing fromneutral position blocking fluid communication between said inlet portand both service ports to either of two operating positions selectivelycommunicating said service ports with said inlet and return ports; and apair of combination relief-check valve assemblies normally closingcommunication between the respective service ports and said return portand in- 3 each other by a straight passage there'between which isconnected to said return port so that fluid under pressure relieved byone spring-biased valve member from one service port to said return portpasses through said straight passage to impinge on the otherspring-biased valve member tending to move the latter to establish fluidcommunication between said return port and the other service port.

4. In combination, a directional control valve comprising a housinghaving an inlet port for fluid under pressure, a return port, and atleast one service port, and a valve member movable in said housing fromneutral position blocking fluid communication between said inlet andservice ports to either of two operating positions selectivelycommunicating said service port with said inlet and return ports; and acombination relief-check valve assembly including a main valve membernormally closing communication between said return and service ports,spring means for yieldably maintaining said main valve member in suchclosed position, said spring means being operative to permit said mainvalve member to be moved as a check valve member by fluid under pressurein said return port of magnitude exceeding that in said service port toa position establishing fluid communication between said ports, andmeans operative to permit said main valve member to be moved as a reliefvalve member by fluid under pressure in said service port of magnitudeexceeding that in said return port to a position similarly establishingfluid communication between said ports; said assembly comprising a bodydetachably secured to said housing and having a service port forconnection with a fluid motor in register with the service port of saidhousing and a return passage in said body that registers with an openingin said housing leading to said return port.

5. In combination, a directional control valve comprising a housinghaving an inlet port for fluid under pressure, a return port, and a pairof service ports, and a valve member movable in said housing fromneutral position blocking fluid communication between said inlet portand both service ports to either of two operating positions selectivelycommunicating said service ports with said inlet and return ports; apassage directly communicating said service ports with each other, and apair of combination relief-check valve assemblies normally closingcommunication between the respective service ports, through saidpassage, said combination relief-check valve assemblies includingspring-biased valve members arranged to be moved as check valve membersby fluid under pressure in said passage of magnitude exceeding that inthe respective service ports to positions establishing fluidcommunication between said passage and the respective service ports, andto be moved as relief valve members by fluid under pressure in therespective service ports of magnitude exceeding that in said passage toa position similarly establishing fluid communication between therespective service ports and said passage; said valve assemblies beingoppositely disposed so that fluid under pressure relieved by onespring-biased valve member from one service port to said passageimpinges on the other spring-biased valve member tending to move thelatter to establish fluid communication between said passage and theother service port.

6. The combination of claim 5 wherein said return port is also incommunication with said passage between said combination relief-checkvalve assemblies, whereby said combination relief-check valve assembliesalso normally close fluid communication between the respective serviceports and said return port, and said spring-biased valve members arealso adapted to be moved as check valve members by fluid under pressurein both said passage and said return port of magnitude exceeding that inthe respective service ports to positions establishing fluidcommunication between said passage and return port and the respectiveservice ports, and to be moved as relief valve members by fluid underpressure in the respective service ports of magnitude exceeding that insaid passage and return port to a position similarly establishing fluidcommunication between the respective service ports and said passage andreturn port.

7. The combination of claim wherein said means operative to permit saidmain valve member to be moved as a relief valve member comprises achamber in which said main valve member is slidably received, an orificeextending through a portion of said main valve member for establishingrestricted fluid communication between said chamber and said serviceport, the portion of said main valve member normally closingcommunication between said passage and service ports being solid, and aspringbiased pilot relief valve means operative to vent said chamber tosaid return passage more rapidly than fluid can be replenished into saidchamber through said orifice when fluid under pressure in said serviceport is of a mag nitude exceeding that in said passage as aforesaid.

8. In combination, a directional control valve comprising a housinghaving an inlet port for fluid under pressure, a return port, and a pairof service ports, and a valve member movable in said housing fromneutral position blocking fluid communication between said inlet portand both service ports to either of two operating positions selectivelycommunicating said service ports with said inlet port and return port;conduits for establishing fluid communication between said inlet portand a discharge port of a pump and between said service ports and therespective ports of a double acting fluid motor; a passageway directlyinterconnecting said service ports; and a pair of combinationrelief-check assemblies normally closing communication between therespective service ports and said passageway and including spring-biasedvalve members arranged to be moved as check valve members by fluid underpressure in said passageway of magnitude exceeding that in therespective service ports to positions establishing fluid communicationbetween said passageway and the respective service ports, and to bemoved as relief valve members by fluid under pressure in the respectiveservice ports of magnitude exceeding that in said passageway to aposition similarly establishing fluid communication between therespective service ports and said passageway, said valve assembliesbeing oppositely disposed so that fluid under pressure relieved by onespring-biased valve member from one service port to said passagewayimpinges on the other spring-biased valve member tending to move thelatter to establish fluid communication between said passageway and theother service port.

9. In combination, a directional control valve comprising a housinghaving an inlet port for fluid under pressure, a return port, and a pairof service ports, and a valve member movable in said housing fromneutral position blocking fluid communication between said inlet portand both service ports to either of two operating positions selectivelycommunicating said service ports with said inlet and return ports; apassage between said service ports, and a pair of combinationrelief-check valve assemblies normally closing each end of said passageand including spring-biased valve members arranged to be moved as checkvalve members by fluid under pressure in said passage of magnitudeexceeding that in the respective service ports to positions establishingfluid communication between said passage and the respective serviceports, and to be moved as relief valve members by fluid under pressurein the respective service ports of magnitude exceeding that in saidpassage to a position similarly establishing fluid communication betweenthe respective service ports and said passage, said valve assembliesbeing oppositely disposed, whereby the fluid relieved by onespring-biased valve member increases the pressure in said passagetending to open the other spring-biased valve member.

References Cited UNITED STATES PATENTS 2,954,011 9/1960 Krehbiel1376l2.1 X 3,023,584 3/1962 Markovich l37596.l3 X 3,077,898 2/1963Raymond l3749l HENRY T. KLINKSIEK, Primary Examiner.

M. CARY NELSON, Examiner.

1. IN COMBINATION, A DIRECTIONAL CONTROL VALVE COMPRISING A HOUSINGHAVING AN INLET PORT FOR FLUID UNDER PRESSURE, A RETURN PORT, AND A PAIROF SERVICE PORTS, AND A VALVE MEMBER MOVABLE IN SAID HOUSING FROMNEUTRAL POSITION BLOCKING FLUID COMMUNICATION BETWEEN SAID INLET PORTAND BOTH SERVICE PORTS TO EITHER OF TWO OPERATING POSITIONS SELECTIVELYCOMMUNICATING SAID SERVICE PORTS WITH SAID INLET AND RETURN PORTS; AND APAIR OF COMBINATION RELIEF-CHECK VALVE ASSEMBLIES NORMALLY CLOSINGCOMMUNICATION BETWEEN THE RESPECTIVE SERVICE PORTS AND SAID RETURN PORTAND INCLUDING SPRING-BIASED VALVE MEMBERS ARRANGED TO BE MOVED AS CHECKVALVE MEMBERS BY FLUID UNDER PRESSURE IN SAID RETURN PORT OF MAGNITUDEEXCEEDING THAT IN THE RESPECTIVE SERVICE PORTS TO POSITIONS ESTABLISHINGFLUID COMMUNICATION BETWEEN SAID RETURN PORT AND THE RESPECTIVE SERVICEPORTS, AND TO BE MOVED AS RELIEF VALVE MEMBERS BY FLUID UNDER PRESSUREIN THE RESPECTIVE SERVICE PORTS OF MAGNITUDE EXCEEDING THAT IN SAIDRETURN PORT TO A POSITION SIMILARLY ESTABLISHING FLUID COMMUNICATIONBETWEEN THE RESPECTIVE SERVICE PORTS AND SAID RETURN PORT; SAID VALVEASSEMBLIES BEING OPPOSITELY DISPOSED SO THAT FLUID UNDER PRESSURERELIEVED BY ONE SPRING-BIASED VALVE MEMBER FROM ONE SERVICE PORT TO SAIDRETURN PORT IMPINGES ON THE OTHER SPRING-BIASED VALVE MEMBER TENDING TOMOVE THE LATTER TO ESTABLISH FLUID COMMUNICATION BETWEEN SAID RETURNPORT AND THE OTHER SERVICE PORT..